This is a project that I am developing, modular and based on AVR:https://www.youtube.com/watch?v=FaunbXS9z4A
Configured with the default MAME keys for two players, the idea is that it can be reconfigured from an I2C LCD to save in the EEPROM.
It is the continuation of another development that I made exclusively for PS / 2, now modular and with the help of Soraer's NKRO USB Converter, it would reach all MiSTer cores that allow the use of keyboard, such as computer cores.
Each Joy2PS2 Core module allows a DB9 type connection that accepts multiple Joysticks protocols such as Atari, SMS, NES, etc ... although combining two Joy2PS2 Core could design a PCB for the Neogeo DB15 protocol, for example. Other PCBs other than DB9 could also be designed, with specific NES connectors, among others. You could even connect 4 modules of Joy2PS2 Core for 4 DB9 players.
All this is possible thanks to the management of the collision of events through buffers when the PS / 2 port is in use.
Each Joy2PS2 Core carries an Atmega168, which works with an internal oscillator of 8Mhz each, which is currently valid. Depending on future needs, this module could be extended to a 16Mhz external oscillator and/or other compatible AVR such Atmega328.